Control for vapor generators



Oct. 2, 1934. P. DICKEY 1,975,085

CONTROL FOR VAPOR GENERATORS Filed Nov. 10, 1931 3 Sheets-Sheet l INVENTOR Paul S. Dickey ATTO EY I Fig.1

Oct. 2, 1934. I p 5 Y v 1,975,085,

- CONTROL FOR VAPOR GENERATORS- Filed Nov. 10. 1931 s Sheets-Sheet 2 INVENTOR Paul 5. Dickey. m

7MTITOR Y 0d. 2, 1934. s, DlcKEY 1,975,085

CONTROL FOR vAPoR GENERATORS Fild Nov. 10, 1931 3 Shams-sheet 3 INVENTOR Paul S. Dickey.

Patented Oct. 2, 1934 UNITED STATES PATENT OFFICE 1,975,085 CONTROL FOR VAPOR GENEBA' IO RS Paul S. Dickey, Cleveland, ()hio, assignor to Bailey Meter Company, a corporation of Delaware Application November 10, 1931, Serial No. 574.0 0

.5 Claims.

This invention relates to a method and means for controlling the operation of vapor generators,

boiler, Serial No. 357,419, filed in the United States Patent Oflice .April 23, 1929 by James Fletcher, and the application of Howard J. Kerr entitled Steam boiler, Serial No. 450,348 filed in the United States Patent Ofiice May '1, 1930;

the present invention being in the nature of an improvement thereto, as well as also being related and in'the nature of an improvement to the co-pending joint application of James-Fletcher and Paul S. Dickey entitled Vapor generator and method and means for operating ,the same, Ser. No. 574,076 filed of even date herewith. It is to be'understood that throughout the specification, where I refer to boilers or vapor generators,

I mean the same.

In vapor generators of the character mentioned having a once-through fluid flow path without circulation and wherein the liquid volume is always at a minimum, the liquid inflow must o1, necessity He continuous and at all times proportioned to the demand or generator load. Furthermore this .typepf unit, having no substantial reserve liquid'capacity and the fluid in motion in the circuit varying\from. liquid to vapor with intermediate percentages of vapor and liquid mixture, cannot be equipped with-any liquid level indicating device such as the standard water glass to establish a safe operating condition. Vapor is generated in tubes as needed and the liquid is fed to the tubes at such a rate thatthe desired proportion is held in a tube between liquid and 'vapor, so that vapor of the desired amount and quality may be obtained. A method and means for operating such a vapor generator in accordance with varying conditions must be provided.

Such a method and means desirably providing for the supply of liquid and heat in proportion to the demand upon the generator for vapor, and such supply desirably readjusted in accordance with other variables such, for instance, as fluid temperature at a location in the flow path just beyond the saturation line, or outlet vapor pres- 4 J 4 I I have .found that constant predetermined quality or temperature of the vapor outflow may be insured regardless of the rate of outflow, through the maintaining substantially constant of the percentage of the fluid'flow path within the boiler in which vapor alone exists. The'point of conversion to complete vapor state, beyond which in the flowpath the fluid exists as vapor only, tends to move along the flowpath through several causes such, for example, as variation in the rate of liquid inflow relative to the rate of vapor outflow, and variation in the rate of supply of the elements of combustion for heating or causing change of state or temperature of the fluid.

One object of my invention in connection with a vapor generator of the drumless or once- -through type is the control of liquid inflow there- 'to, proportionate to an indication of load on, or output of, the generator.

A further object is to control the liquid inflow.

to maintain substantially constant, regardless of rate of vapor outflow, the percentage of fluid flow path within the boiler wherein exists the fluid as a vapor only.

Another object is to control the liquid inflow proportionate to an indication of load upon the boiler, with readjusting or modifying control of the liquid inflow from temperature indication at a location along the fluid flow path.

Still another object is to control the supply of an element of combustion proportionate to an indication of load on the boiler and to readjust such supply from an indication of vapor outlet pressure. K

A still iurther'object is to proportion the supply of an element of combustion to the supply of a second element of combustion for most efficient combustion.

A still further object is to so coordinate the control of liquid inflow and. the supply of the elements of combustion as to most efilciently provide a vapor. outflow from the boiler of desired quantity and quality. 5

' In the illustrative embodiments of my inventign, I show herewith:

Fig. 1 is a sectional elevation of a vapor generator according to the present invention, com

bined with-the requisite apparatus to control the Fig. 3 is similar to Fig. 2 to illustrate a third embodiment of the invention.

In the various drawings, identical parts bear the same reference numerals.

Referring now in particular to Fig. 1, I have illustrated a steam generating boiler 1, having a furnace 2 for heating fluid passed through a multiplicity of conduits in heating relation with the combustion and products of combustion. The elements of combustion such as fuel and air, for example, are fed to the furnace '2, in regulated amount through the conduits 3 and d'respectively. The conduit 3 is adapted, in the present embodiment, to supplyoil for combustion to the furnace I meter 6. Thefconduit 4 for supplying air' for combustion to the furnace 2 is fed by a blower '2'!" which is driven by a motor 8, at a speed depending upon the controlled position of a rheostat ,9;

inserted in the electric circuit of the motor.

Liquid to be converted into vapor under pressure is fed to a header 10 through a conduit 11 by a pump 12, driven by a motor 13 at a speed depending upon the regulated position of a rheo=-. stat i l inserted in the electric circuit of the motor.

From the header 10 originate three parallel conduits 15, 16 and 17, each of series type and which are of small diameter and great length, being formed sinuously in layers by suitable bench ing, in a water heating or economizer section 18 of the flowpath, the lower portions of which having much greater length than the upper portions and which extend outwardly into the walls of the flue passage for support. From the econo mizer section 18, the parallel conduits lead to'a header 19, and from the header 19, enter the furnace at" 20, whereafter they are coiled upwardly surrounding a secondary combustion space of the furnace. A certain portion of the surrounding conduit wall comprises a steam generating portion 21 while the uppermost portion of the surrounding conduits comprise a superheating section 22, from which the parallel conduits lead to a header 23, from which there passes a conduit 24, through a controlor throttle valve 25, to a turbine or other utilizing apparatus 26. Prodnets of combustion pass from the furnace 2 in series heating contact with the steam generating portion 21, the superheating portion 22 and the N economizerportion 18 to a stack 27, whose draft is controlled by the positioning therein of a damperl28 through the medium of linkage 29 controlled in parallel with the rheostat 9.

It will be observed that the grouping of the parallel conduits is definitely segregated into three sections; namely, an economizer section 18, a generating section 21 and a superheating sec= tion 22, whereinthe fluid flowing through the conduit is continuously in heat relation with the products of combustion passing from the furnace. Equalizing headers 19, 30 and 31 are shown in the flow path to bring the fiuid of the several conduits into mixing relation to commingle and current to the hot gases passing thereover, while other portions thereof have fluid flow with the gases passing thereover concurrently.-

The grouping of the conduit sections and their arrangement with respect to the furnace, secondary combustion chamber, and flue, is such that insofar as arrangement is considered, the heat absorbed by any one conduit is substantially equai to the heat absorbed by any other conduit, with the result that heat input to each conduit for a given combustion condition is approximately constant and the furnace and flue are constructed so that the heat stored therein is at a minimum.

In the operation of such a vapor generator, certain variables are indicated andutilized as the basis for automatically controlling the supply "of fluid thereto and the supply of the elements of combustion to the heating furnace.

ll indicate at 32 a pressure responsivedevice such as a Bourdon tube connected to the conduit 24 and having an indicator pointer 33 adapted to co-operate with an index 34 for advising the in; stantaneous value of the vapor outlet pressure.

At 35 is indicated a device positioned responsive to temperature such, for example, as -an electrical instrument of known type, connected tively to contact with separate portions or the conduit and sensitive to temperature of the fluid at selected points in its path. Preferably the thermocouple 38 is located to be sensitive to temperature in the generator section, namely temperi ature of a mixture of liquid and vapor corresponding to the pressure, while the thermocouple 4c is positioned to be sensitive to temperature of the fluid in the superheater portion, namely being beyond in the direction of fluid flow the location in the flow path of conversion to complete vapor state and where the vapor may be slightly superheated.- The temperature responsive apparatus may be of any known commercial type solong as an indicator 41 is positioned relative to index 12 to advise the instantaneous value of the temperature in the fluid flow path at a selected location.

As an indicator of generator output or load upon the generator, I utilize the position of the throttle valve 25 whose handle has an extension forming a pointer 43, cooperating with an 5 index 44. The throttle valve '25 being of a calibrated type to the end that the indication of the pointer 43 relative to the index 44 is representative of the rate of flow of vapor therethrough as a measure of the generator output or 12;)

load.

I preferably primarily control the liquid inflow to the boiler by means of the ,rheostat legend the fuel supplied for combustion to the furnace by means of the control valve 5, directly proportional to an indication of output, namely, in the present illustration; the position of the throttle valve 25. To this end, I connect to the throttle valve handle a depending rod 45, freely pivoted to one end each of two beams 46, 4'1, the latter pivotally connected at its other end to be positioned by the Bourdon tube 32, and the former pivotally connected at its other end to be freely positioned with the pointer 41, to the end that the beam 47 is positioned along a definite path in a plane of space jointly by throttle posi- 'tion and by vapor outlet pressure. The beam 46 being positioned likewise along a definite path in a plane of space, jointly by throttle position 52, throughthe agency of a motor 53, which in itself is connected in the circuit including the said contacts. A beam 54 oscillatable around the.

center 52 by rotation of the motor 53, at one end carries the contactor case 51 and at the other end has pivotally connected thereto a rod 55, for

positioning the fuel control valve 5.

The circuit of the pilot motor 53 and the contactor 51 is similar to the one disclosed and claimed in the co-pending application Serial No.

561,005 filed September 3, 1931, by John D. Ryder entitled Motor control circuits, and embodies the use of thermionic valves connected'in an alternating current circuit, and arranged each to pass a pulsating direct current comprising onehalf of the alternating current wave. The field of the motor 53 is energized across a source of direct current, while the am .ture is in an alternating current circuit, comprising thermionic valves 56 and 57 whose grid circuits are respeclvely controlled by the contacts of the contactor 51, normally close-circuited, to the end that the armature of the motor 53 is normally energized in the alternating current circuit. The opposing equal, torques of the alternating current halfwaves prohibit rotation of the armature and thermal damage to the motor is prevented through the use of a reactor 58. When the grid control circuit to either the valve 56 or the valve 57 is open-circuited as by the contactor 51, that valve ceases to pass current and the torque on the motor armature from the pulsating direct current passing through the other valve causes rotation of the said armature in desired direction. The arrangement is such that when the rod 48 is moved downwardly, then (on the drawings) the left hand contact is open-circuited and the motor 53 is caused to rotate in a direction wherein the contactor case 51 is moved downwardly until the left hand contact is again 'close-circuited, whereupon a substantially instantaneous application to the armature 53 of opposing equal torques of the full-wave alternating current causes substantially instantaneous plugging or stoppage of rotation thereof. Simultaneously, the motor has caused a positioning of the fuel control valve 5 in desired amount.

A similar arrangement is shown. in connection with the operation of the rheostat 14, wherein the beam 46 whose position is determined responsive to position of the throttle valve 25 and of the temperature device 35, causes vertical movement of a freely depending rod 59 to position a contactor bar 60, resulting in rotation of the motor 61 in a desired direction for regulating the rheostat 1-4 and balancing back on the contactor 60 to cause a stoppage of rotation of the motor 61.

Having controlled the supply of fuel to the furnace, primarily in accordance with an indication of boiler output and secondarily from an indication of vapor outlet pressure, I utilize the rate of supply of fuel to the furnace as a guide to the supply of air for combustion and do this by separately measuring therate of supply of fuel and the rate of flow of air, balancing one of the measures against the other to determine the ratio thereof, comparing the ratio to a predetermined desirable ratio, and upon departure of such ratios effecting acontrol of the forced draft fan motor 8 and the uptake damper 28, through a positioning of the rheostat 9, and the linkage 29 respectively, through the agency of a pilot motor 62.

The pilot motor 62 is similar to the pilot motors 53 and 61 above described, and is in an alternating current circuit controlled by thermionic valves, in turn controlled by a contactor whose position is responsive ,to departure of the ratio between fuel supply and air supply from predetermined desirable ratio. The motor circuit is further arranged for speed control wherein the speed of the motor 62 varies depending upon the magnitude of departure of the ratio between fuel supply and air supply from a predetermined ratio. Features of the thermionic valve control circuit for the motor 62 are similar to the circuit of the motors 53 and 61 disclosed and. claimed in the referred. to application of Ryder; Serial No. 561,005, while-further features of the circuit comprising .the speed control of the-reversing pilot motor 62 are disclosedand claimed in a co-pend' ing application of John D. R der, entitled Motor control circuits, Serial No. 561,006, filed September 3, 1931. The latter referred to applicathe grid circuit of each of the thermionic valves' through an upper contactor bar 65, and the 'variable reactance 63 through movement of a lower contactor bar 66. The contacts carried by the lower bar 66 relative to those carried by a case 6'], when open-circuited'one or the other, result in the positioning of a self-starting synchronous motor 68 in one direction or the other through the releasing thereof of one of two opposing equal torque fields normally both energized, and at the same time, the positioning of the contactor case 6'7 causes the positioning of a core in a reactance 63 for speed control of the motor 62. Certain features of the contactor 64 are disclosed and claimed in a c'o-pending application Serial No. 589,009 filed January 26, 1932 by Walter E. Dueringer.

For positioning the contact bars and 66, I provide' a freely, pivoted rod 69, pivotally suspended from intermediate the ends of a floating beam 70. One end of the beam '70, namely (in the drawings) the right hand end, is pivotally suspended from a rod '71, in turn pivotally suspended from the pointer '72 of the flow meter 6, which pointer cooperates with an index 73.

The flow meter indicated in general at 6 for providing a measure of the rate of supply of fuel to the furnace is of a known type, such as is disclosed in the patent to Ledoux No. 1,064,748 grantbell having walls of material thickness and shapedas described and claimed in the above mentioned Ledoux patent.

. Effective upon the left hand end of the floating beam for positioning the same, is pivotally connected thereto a rod '74. suspended from abeam '75 which is, in turn, pivoted intermediate its ends and carries a pointer '76 adapte dto cooperate with an index '77, to indicate thereon the rate of flow of air through the passages of the vapor generator. From the oscillatable beam '75, are suspended two liquid sealed inverted bells as well as a displacing member, the whole comprising a rate of flow meter such as is well known in the art, wherein the positioning of the system comprising the bells, the displacer and the beam 15, is responsive to a pressure-differential transmitted to beneath the bells through pipes '78, '79, leading respectively above and below the economizer section 18 through which is a drop in pressure in known relation to the rate of flow of the air and products of combustion therethrough.

By air flow, I intend to mean the excess of air as well as the products of combustion which pass through the restriction of the economizer section 18, to cause a pressure differential there across, bearing a known relation to the rate of flow therethrough. I have found that by so measuring the total flow of air and products of combustion leaving a furnace such as 2, I have a definite guide or measure of the rateof supply of air for combustion when the system is properly calibrated. I

In operation, it will be seen that the disclosure provides a method and means for the control of liquid input to the boiler from a' relation between boiler output and temperature at a location along the fluid flow path; a control of the supply of fuel to the furnace responsive to an indication of boiler output and to vapor outlet pressure; and a' control of air for combustion in accordance with the rate of supplyof fuel to the furnace.

Assume that the system is in operation with liquid inflow to the header 10 substantially equal to vapor outflow through the conduit 24; the

quantity and quality of the outflow vapor as desired and the supply of the elements of combustion in desired proportion for most'eflicient operation. Assume now that by hand control of the throttle valve. 25, an increase in output of the boiler is made, then through the automatic control system a positioning of the rod 45 results, through the pilot motors 53 and 61 and their related control circuits,'in a positioning of the fuel control valve 5 and of the rheostat 14 in desired proportion, wherein the rate of supply of fuel and liquid to the furnace and boiler respectively is increased proportionate to the increase in output of the boiler. The flow meter 6 responsive to the rate of input of fuel to the furnace causes a positioning of the rod 69 to result, through the pilot motor 62, in a positioning of the rheostat 9 and the linkage 29 wherein the rate of air supplied for combustion is readjusted to remain substantially equal to or proportionate to the supply of fuel for combustion.

Should the vapor outlet pressure to which the Bourdon tube 32 is responsive vary from desirable value, either simultaneously with a variation in boiler output or otherwise, a positioning of the fuel control valve 5 will result to cause the proper-variation in rate of fuel supply and heat input to the furnace and boiler for restoring the pressure to its predetermined desirable, value.

Simultaneously such change in rate of supply of fuel will cause, as above described, a change in the rate of supply of air for combustion, whereby the combustion is always accomplished in most eflicient manner.

mvaoec Effective upon the rate of supply of liquid to the boiler, in addition to the position of the throttle valve 25 as a main load control for paralleling the liquid input and the vapor output, is the device 35 responsive to a selected tempera: ture at a location inthe conduit or fluid flow path. Preferably I control the rate of supply of liquid inflow to the boiler from the location along the flow path beyond'the point of complete conversion to'vapor state as indicated, for example by the location of the thermocouple 40, just within the superheater section or portion of the conduit. I have found that primarily in the control of a boiler such as is described, it is essential in maintaining the vapor outflow in desired quantity and quality, that I maintain a fixed percentage of the flow path or conduit to have vapor only being superheated and it will be seen that the best way to so maintain the predetermined portion of the flow path as desired, is to proportion the inflow of liquid to the output of the boiler as I have explained and readjust the inflow from a temperatureat a location in the fiow path, which temperature will vary responsive to a change in the amount 6f the flow path which I desire to have I remain constant.

Forexample, if the thermocouple 40 is sensitive to temperature just beyond the point of complete conversion to vapor state, then it will be sensitive to a temperature which is equal to the temperature corresponding to pressure plus whatever superheat is present in the vapor. Such a location has preference over a thermocouple located exactly at thepoint of complete conversion to vapor state, for until the vapor begins to be superheated, there is no temperature change between that of the liquid and that of the vapor so that it is not prac- 'tical to attempt to determine exactly the location in the flow path of complete conversion to vapor state. I provide, however; the thermocouples 38, 39 which I may use as a checking control upon the supply of liquid input to the generator through the selectivity of the switch 37, if desired.

In Fig. 2, I illustrate an embodiment of my invention similar to that of Fig. 1 except that I employ hydraulic means for the positioning of the various controlled factors rather than the electric means just described. The vapor generator illustrated in general at 1, is shown in side elevation rather than in sectional elevation. The internal construction is the same as in Fig. 1 except that I have dispensed with the equalizing or mixing boxes 19, 30 and 31. I supply a liquid to the boiler through a conduit 11, and the vapor outflow from the boiler passes through the conduit 24, having a throttle valve 25 for the control thereof. Fuel is supplied to the furnace through a conduit 3 and air through a conduit 4 as in Fig. 1.

. The position of the throttle 25 is transmitted through linkage 80 to one end of a beam 81, the other end of which is positioned by vapor. outlet pressure for the control of a pilot valve 82 to cause a positioning of a hydraulic power piston 83 for adjusting the fuel regulating valve 5.

The linkage 80, representative of throttle position, is further effective in positioning a beam 8 4, the other end of which is positioned responsive to temperature at a location in the fluid flow..path, and effective for the positioning of a pilot valve 85 controlling a hydraulic power piston 86 to move the rheostat 14 for control of the liquid inflow pump' 12.

The fuel supply meter 6 and the air supply meter '75 are similar to those shown in Fig. 1 and serve to control a pilot valve 87 for positioning 150 the hydraulic power piston 88, for regulating the air supply dampers.

It will be seen then that the arrangement of equipment for indicating the instantaneous value of the variables and the equipment for utilizin such indications to control the supply of liquid input and the elements of combustion, is similar to that I have described in detail in Fig. 1', except that herein I utilize hydraulic power pistons controlled by pilot valves. Y

In Fig. 3, I illustrate a similar embodimentto those of Fig. 1 and Fig. 2, differing therefrom only in that herein I employ a combination 'of selfsynchronous electric motor remote positioning devices for transmitting the position corresponding to the instantaneous value of the variables to the point of control wherein desirable cortrol is attainedthrough hydraulic means.

I indicate such self-'ynchronous or Selsyn transmitting generators for transmission of position at 89, 90, 91, 92 and 93, while the selfsynchronous receiving motors are indicated at 94,

95 and 96. The transmitting generator in each case is operated at a suitable angular rotation of the order of 30 degrees maximum ,through angular positioning of the rotor or single-phase field winding. The stator or armature is in each case pro-- vided with a three phase winding. The field windings of each transmitting generator are energized I from a suitable source of alternating current supply. The rotor of the transmitting generator .89 is positioned responsive to throttle position, that of the generator 99 responsive to the vapor outlet' pressure, that of the generator 91 responsive tothe air flow,'that of the generator 92 responsive 'position of the rotor 89 to rate of fuel supply, and the rotor of the generator 93 responsive to temperature at a location in rotor positioned responsive to a differential be-.

tween the position of the rotor 91 and that of the rotor 92, or corresponding to the relation between air supply and fuel supply. Correspondingly, the receiving motor 95 has its rotor positioned responsive to a differential between the and that of the rotor 90, or dependent upon the throttle position modified by vapor outlet pressure value. The rotor of the receiving motor 96 is positioned responsive to the throttle position from the transmitting generator 89 modified through the agency ,of the transmitting generator 93 representative oi. temperature at a location in the fluid flow path.

The operation of systems of this general character for the transmission of angular movement is well known in the art. Voltages are induced in the three-phase stator windings of the generator and motorby the single-phase field winding on the associated generator rotor. When the rotor of either of the related motors is moved from a predetermined position with respect to its stator,

a change is efiected in induced voltage in the armature windings and the rotor of the receiving motor assumes a position of equilibrium relative to the transmitting generators wherein the induced voltages in the three-phase windings are equal and opposite, and consequently no current is set up in the armature winding. If the rotor of one of the generators is turned and held in a new position, the voltage is no longer counterbalanced, whereby equalizing currents are caused to flow inthe armature windings. The equalizing currents exert a torque on the rotor of the receiving motor, causing it to take up the position corresponding to a differential between the position of the transmitting generators. Angular movement imparted mechanically to the rotors of the transmitting generators 89 and result in an angular positioning of the rotor of the receiving motor 95. Similar action occurs between the transmitting generators 89, 93 and the receiving motor 96; and between the transmitting generators 91, 92 and the receiving motor 94.

The fuel 011 control valve 5 positioned through hydraulic piston 83 is controlled in its positioning the fluid flow path. Linkage connecting the rotor of the motor with the pilot 82 and the power piston 83 provides a balanced follow-up wherein movement of the pilot 82 resulting in movement of the power piston 83 causes a repositioning of the pilot 82 to shut off position, so that a control is provided commonly known as positioning control wherein each position of the rotor of 95 results in a definite positioning of the power piston 83 and correspondingly of the throttle valve 5.

Control of the liquid input to the vapor generator is accomplished through regulation of the rheostat 14 from the power piston 86, controlled through the pilot 85 from position of the rotor 96, which is set up by throttle position from 89 and modified by 93, an indication of temperature at a location along the fluid flow path.

.A balance is established between rate of fuel supply and rate of air flow as indicated by the rotor positions 92 and 91 wherein if said balance is obtained, the rotor position whereinthe pilot 8'7 is in shut-off position. Should the balance deviate in one direction or the other from that desired, the rotor 94 is positioned in proper direction to move the pilot 8'! wherein the power piston 88 is moved to cause a change in the value of air flow for positioning the rotor 91 to cause the rotor 94 to move the pilot 8'? to shut- -ofi position.

In general, in the operation and control of such avapor generator and furnace, I contemplate a method and means for controlling the liquid 94 is in a predetermined inflow and supply of elements of combustion in the most eificient manner for insuring a vapor outflow of desired quantity and quality. The control of such a drumless vap r generator as I have described, presents a problem differing considerably from the ordinary storage type of vapor generator and it is necessary to appreciate in connection therewith the fact that in each conduit comprising a fluid fiow path through the generator, there will be at all times a location which I term the vaporization line, at the inlet side of which is the water heating section and at the outlet side, a combination of vapor and liquid. There is further in the series flow path a location which I designate as the saturation line? or point of conversion to complete vapor state beyond which exists vapor only. A water heating or economizing portion of the fluid flow path is first in the series flow before the vaporization generator or heating surface. Between the section, is vapor vaporization line and the saturation line exists a;

mixture of vapor and a liquid, and beyond the saturation line, in what I term the superheater only in varying degree of superheat. 1

One of the main features of my invention is "the discovery that by maintaining substantially constant the percentage of the fluid flow path comprising the superheatef section beyond the location in'the fluid flow path of complete conversion to vapor state, regardless of rate of output of the boiler, I will maintain substantially constant the quality of the vapor outflow. The temperature of the vapor at the saturation line will be the same as the temperature just preceding the line for it will be the temperature corresponding to the pressure, regardless of whether at that point exists liquid or vapor. Beyond the saturation line, however, where vapor; only exists and is still subjected to the heating eifect of the furnace and products of combustion, the vapor may have a temperature superheated or substantially higher than that at the' point of complete conversion to vapor state and usually progressively higher from the saturation line to the point of outflow from the generator. Thus, by taking a temperature measurement in the flow path just beyond the saturation line, I obtain a temperature which is indicative of complete vapor state with a slight amount of superheat and by using this temperature as the readjusting control, in regulating the supply of liquid inflow to the fluid flow path, wherein the primarycontrol of liquid inflow is in ac cordance with boiler output or throttle position, I accomplish my desirable feature of maintaining substantially constant the portion of the fluid flow path'where'in exists vapor only.

I have illustrated and described the use of the selective switch 3'7 whereby I may utilize as a corrective influence a temperature selective between a multiplicity of locations in the fluid path and I have such possible selection for the purpose of basically changing the amount or portion of the fluid flow path wherein exists vapor only, through the control selectively from cheer the said temperatures and for thepurpose of selecting between desired 'quality of the outflowing vapor. Thus for example, should I desire the vapor outflow to have a temperature of 250 F. represent'-,

ing a certain amount of superheat, I may control to maintain acertain portion of the flow path to have vapor only therein such, for examplefas that portion slightly greater in length than from the location of the thermocouple 40 to the exit from the boiler. If, however, I desire to control for a slightly. different temperature of the vapor leaving the boiler, I may utilize the thermocouple 39, thereby increasing the percentageof the fluid flow path wherein exists vapor only.

I show in Fig. 1 three parallel conduits-com- ,prising three similar fluid flow paths'through the boiler with the utilization of'equalizing or mixing boxes at various points along the path. In Fig. 2 and Fig. 3, ,1 show two parallel conduits and in Fig. 2, they are carried completely through the boiler as separate flow paths having no equalizing boxes. It will be apparent that I am not limited in my invention to two or three flow paths nor to the use'of equalizing boxes but I contemplate broadly the utilization of one or more conduits comprising a continuous fluid flow path wherein liquid under pressure enters at one end and vaporof desired quantity and qualityis discharged from the other end, without storage'or circulation.

Having thus described my invention in preferred embodiments thereof, I desire it to be distinctly understood that I am not to be limited thereby except as to the claims in view of prior art.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. Apparatus for automatically controlling the operation of a vapor generator having a oncethrough fluid'passage receiving liquid at one end and delivering superheated vapor at the other and heated by elements of combustion, comprising in combination, a generator output indicator, a thermostat sensitive to temperature at a location in the passage wherein is superheated vapor; a control circuit comprising a motor having a field winding and an armature, a source of direct current for energizing the field winding, the armature connected in an alternating current circuit, two thermionic valves in the armatu're circuit, such valves oppositely connected in parallel with each other and in series with the armature, the valves normally effective to pass full-wave alternating current to the armature for opposing equal torques whereby the armature is held from rotation; and control means positioned by said indicator and by-said thermostat for selective'y making ineffective either of said valves to' effect a rotation of the armature in a. desired direction, said motor adapted to regulate the rate of liquid inflow to the generator.

'2. Apparatus for automatically controlling the operation of a vapor generator having a once through fluid passage receiving liquidat one end and delivering superheated vapor at the other and heated by elements of combustion, comprisingin combination, a generator output indicator, a thermostat sensitive to temperature at a location in the passage wherein is superheated vapor, a pressure indicator positioned responsive to vapor outlet pressure; a control circuit comprising a motor having a field winding-andilan armature, a source of direct current for energizing the field winding, the armature connected in an alternating current circuit, two thermionic valves in the armature circuit, such valves oppositely connected in parallel with each other and in series with the armature, the valves normally effective to pass full-wave alternating current to the'armature for opposing equal torques whereby the armature is held from rotation; control means positioned by said indicator and by said thermostat for selectively .7 making ineffective either of said valves to eflect a rotation of the armature in a desired direction, said motor adapted to regulate the rate of liquid inflow to the generator, at second similar motor and control circuit therefor, and regulating means positioned by said indicator and by said pressure indicator.

operationpf a vapor generator having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the other and heated by elements pf combustion,

comprising in combination, a generator output" .operation of a heated vapor, a pressure indicator of vapor outlet pressure, and meters of the rate of supply of the elements of combustion, control means including electron discharge devices'responsive to said indicator and to said thermostat and adapted to control the liquid input, control means including electron discharge devices responsive to said indicator and to. said pressure indicator and adapted to regulate the supply of one of the elements of combustion, and control means including electron discharge devices responsive to said meters and adapted to control the supply of another element of combustion.

4. Apparatus for automatically controlling the operation of a vapor generator having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the otherand heated by elements of combustion, comprising in combination, a generator output indicator, a thermostat sensitive to temperature at a location in the passage wherein is superheated vapor, a regulator of the rate of liquid inflow to the generator, and electric means including electron discharge devices interconnecting said indicator, said thermostat and said regulator whereby the regulator is positioned responsive to both the generator output and the said temperature.

5. Apparatus for automatically controlling the operation of a vapor generator having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the other and heated by elements of combustion, comprising in combination, a generator output indicator, a thermostat sensitive to temperature at a location in the passage wherein is superheated vapor,

a regulator of the rate of liquid inflow to the generator, hydraulically actuated means for positioning such regulator, and electric means interconnecting said indicator, said thermostat and said hydraulic means whereby the hydraulic means is positioned responsive to both the generator output and the said temperature.

6. Apparatus for automatically controlling the operation of a vapor-generator having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the other and heated by elements of combustion, comprlsing in combination, a generator output indicator, a regulator of the rate of liquid inflow to the generator, and control means for positioning said regulator, said control means actuated by electron discharge devices responsive to said indicator whereby the regulator is positioned responsive to the generator output.

'7. Apparatus for automatically controlling the operation of a vapor-generator having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the other and heated by elements of combustion, compris-. ing in combination, a generator output indicator, a regulator of the rate of supply of the elements of combustion 'to the generator, and control means for positioning said regulator, said control means actuated by electron discharge devices re-- sponsive to said indicator wherebythe regulator is positioned responsive to the generator output.

8. Apparatus for automatically controlling the vapor-generator having small liquid storage with a high rate of evaporation and heated by elements of combustion, comprising in combination, an indicator of the load on the generator, measuring means of each of the elements of combustion, ratio determining means of said measures; means for comparing the ratio with a predetermined ratio, a regulator of the supply of one of the elements of combustion, control means for positioning said regulator, said control means actuated by electron discharge devices responsive to said ratio comparing means, a second regulator controlling the supply of the second element of combustion, and other control means for positioning said second regulator, said other control means actuated by electron discharge devices responsive to said indicator.

9 Apparatus for automatically controlling the operation of a vapor-generator having small liquid storage with a high rate of evaporation and heated by elements of combustion, comprising in combination, measuring means of each of the elements of combustion, ratio determining means of said measures, means for comparing the ratio with a predetermined ratio, a regulator of the supply of one of the elements of combustion, and control means for positioning said regulator, said control means actuated by electron discharge devices responsive to said ratio comparing means.

10. Apparatus for automatically controlling the operation of a vapor-generator having small liquid storage with a high rate of evaporation 100 and heated by elements of combustion, comprising in combination, a generator output indicator,

an indicator of vapor outflow pressure, a regulator of the rate of supply of fuel to the generator, hydraulically actuated means for positioning said regulator, and electric means interconnecting said indicators and said hydraulic means whereby the hydraulic means is positioned re sponsive to both generator output and vapor outflow pressure. I

-11. Apparatus for automatically controlling the operation of a vapor generator having small liquid storage 'with a high rate of evaporation and heated by elements of combustion, comprising in combination, an air flow meter, a fuel flow meter, 11: a regulator of the rate of supply of air for combustion to the generator, hydraulically actuated means for positioning such regulator, and electric means interconnecting said meters and said hydraulic means whereby the hydraulic means is positioned responsive to metered air flow and metered fuel flow.

12. Apparatus for automaticallycontrolling the operation of avapor-generator having small liquid storage with a high rate of evaporation and heated by elements of combustion, comprising in combination, a generator output indicator, a regulator of the rate of liquid inflow to the generator, and control means for positioning said regulator, said control means actuated by electron discharge devices responsive to said indicator whereby the regulator is positioned responsive to the generator output.

13. Apparatus for automatically controlling the operation of avapor-generator having small liquid storage with a high rate of evaporation and heated by elements of combustion, comprising in combination, a generator output indicator, a regulator of the rate of supply of the elements of 140 combustion to the generator, and control means for positioning said regulator, said control means actuated by electron discharge devices responsive to said indicator whereby the regulator is "posir tioned responsive to the generator output.

14. Apparatus for automatically controlling the operation of a vapor generator having a oncethrough fluid passage recei ing liquid at one end under pressure and delivering superheated vapor 159 storage with a high rate of evaporation and heated by elements of combustion, comprising in combination, a regulator of the rate of liquid infiow to the generator, and control means for positioning the regulator, said control means'actuated by electron discharge devices.

PAUL S. DIY.

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